Flexible printed wiring structure for LED light engine
A lighting engine, system, and method of fabrication are described. The system includes a chassis with a ridge extending from a bottom that defines inner and outer cavities. A flexible printed circuit (FPC) is disposed in contact with a wall of the inner and outer cavities and on the ridge top and is connected to wiring retained within bosses in the outer cavity. LEDs are mounted on the FPC to emit light toward a center of the cavity. A light guide disposed has an edge that opposes the LEDs and receives light emitted by the LEDs. The FPC has a polyimide insulator coupled with a pressure-sensitive adhesive (PSA), a copper layer on the polyimide insulator, and a high-reflectivity white coverlay on the copper layer. Other apparatuses, systems, and methods are also disclosed.
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This application claims the benefit of priority to U.S. Provisional Patent Application Ser. No. 62/837,581, filed Apr. 23, 2019, U.S. Provisional Patent Application Ser. No. 62/846,072, filed May 10, 2019, and U.S. Provisional Patent Application Ser. No. 62/850,959, filed May 21, 2019, each of which is incorporated herein by reference in its entirety.
CROSS REFERENCE TO RELATED APPLICATIONSThis application is related to commonly assigned U.S. patent application Ser. No. 16/729,151, entitled “Alignment Features for LED Light Engine,” U.S. patent application Ser. No. 16/729,162, entitled “LED Light Engine Features,” and U.S. patent application Ser. No. 16/729,175, entitled “Method of LED Light Engine Assembly,” all filed on Dec. 27, 2019.
TECHNICAL FIELDThe present disclosure relates to a light emitting diode light engine.
BACKGROUNDLighting applications can use light emitting diodes (LEDs) as their light sources. Many LED installations use Class 2 circuitry. Class 2 circuitry provides protection from electrical shock and carries no risk from fire. For example, in the US Class 2 compliant power supplies convert a 120V (wall) power into low voltage 12V or 24V using DC drivers that use less that 60V (in dry applications, 30V in wet applications), less than 5 amps, and under 100 W. These considerations may pose restrictions on the number of LEDs a Class 2 driver can operate simultaneously. In a number of lighting systems, however, it may be desirable to increase the number of LEDs used and/or power used by the LEDs, and thus supplied by the power supply, beyond that of Class 2. Thus, additional care may be taken in designing circuitry and installations for non-class 2 lighting systems that are not class 2 compliant.
Corresponding reference characters indicate corresponding parts throughout the several views. Elements in the drawings are not necessarily drawn to scale. The configurations shown in the drawings are merely examples, and should not be construed as limiting the scope of the disclosed subject matter in any manner.
DETAILED DESCRIPTIONNon-Class 2 lighting systems are discussed in detail below. The lighting systems may be suitable for indoor or outdoor applications. Such lighting systems may use LEDs and light-guide technologies to provide lighting because of reduced glare and pleasing appearance when the lighting system is in both an on state, in which one or more of the LEDs of the system provide illumination, and an off state, in which none of the LEDs provide illumination. For example, as described in more detail below, outdoor applications of the LED systems (such as pedestrian path lights) can use fairly expansive batwing-shaped light distributions (e.g., see
As described above, Class 2 lighting systems can be relatively straightforward to design and manufacture due to the relatively low power. However, for relative high-power and/or high voltage (non-Class 2) lighting systems, additional safety-related factors may prove more challenging to meet in a design. Specifically, meeting standards known as, for example, UL8750 approbations standard (in North America) or EN 61347-2-13 and EN61347-1 (in Europe) can create challenges when designing and manufacturing a high-power LED light engine for a non-Class 2 system.
The light engine 100 contains a number of elements connected together with connectors, such as screws or other mechanical fasteners known in the art, or, for example, chemical fasteners such as adhesives. The light engine 100 provides light from LEDs 116a mounted on a flexible printed circuit (FPC) 116 (also referred to as a flexible printed circuit board). In some embodiments, the FPC 116 may be shaped as a circular loop (although other shapes may be used), with the LEDs 116a facing inward toward the center of the loop in some embodiments or outward away from the center of the loop in other embodiments.
The LEDs 116a can thus be mounted or otherwise mechanically supported or adhered by the FPC 116 (e.g., via a direct support requirement (DSR)) as well as being electrically powered by the FPC 116 and positioned to emit light inwards toward a center of the circular loop. The LEDs 116a can be soldered or otherwise electrically coupled onto the FPC 116. Drivers for the LEDs 116a can also be positioned on, or otherwise connected to, the FPC 116. The LEDs 116a, the accompanying circuitry (of the FPC 116 and elsewhere), and mechanical/optical elements can be designed to function at a maximum operating temperature (MOT) of 90° C., 105° C., or any suitable value, as desired dependent on the application and environment in which the light engine 100 is to be used.
The LEDs 116a can be arranged in a line along the FPC 116 (e.g., each LED 116a centered along the same line) or can be arranged in a two-dimensional pattern, such as an array. In some examples, the LEDs 116a can be arranged symmetrically around the FPC 116, with equal spacing around the loop (adjacent LEDs 116a having substantially the same distance therebetween). Such symmetry in some cases may be used to produce a generally uniform output beam. In other examples, the LEDs 116a can be arranged asymmetrically around the flexible printed circuit. One example of asymmetric arrangement may include the LEDs 116a positioned only on one half of the loop, with the other half lacking LEDs 116a (such as being arranged in a semicircle or in any number of segments whose total angular distribution is about 180°). In other examples, the LEDs may cover angular distributions other than about 180° (in any number of segments). Such asymmetry can produce beam shaping, which may be used in applications in which beam-shaping is desirable.
A generally planar, light guide plate (LGP) 112 can be positioned in an interior of the circular loop. The LGP 112 may be formed as a substantially circular disc as shown, or in a multi-sided shape (e.g., octagon) in other embodiments. The shape may be dependent, for example, on the light arrangement desired from light engine 100, in addition to or instead of the LED placement. The LGP 112 may receive light emitted by the LEDs 116a through a circumferential edge of the LGP 112. The LGP 112 can be shaped as a generally planar disc having a circular edge. In some examples, the LGP 112 can have a thickness of about 6 mm and a diameter of about 483 mm (approximately 19 inches). Note that here, as with all other measurements, the measurements are provided at about room temperature (e.g., about 20° C.-25° C.) and have a tolerance associated therewith. In some examples, the LGP 112 can be formed from poly(methyl methacrylate) (PMMA), glass or any other substantially transparent material. When the LGP 112 is formed from PMMA with a thickness of 6 mm can allow the LGP 112 to pass a UL94 V0 requirement, which limits flammability of plastic materials. The UL94 V0 requirement requires burning to stop within ten seconds on a vertical specimen, with drops of particles being allowed as long as they are not inflamed. By forming the LGP 112 from PMMA with a thickness of 6 mm, the maximum operating temperature of the LGP 112 may be greater than 90° C. In some examples, the LEDs 116a can be spaced greater than or equal to 1.6 mm from an edge of the LGP 112. The LGP 112 may have a dispersive pattern (e.g., dots, see
The LGP 112 may rest on a gasket 114 disposed within a chassis 120. The gasket 114 may be supported by the chassis 120 to allow the edge of the LGP 112 to be centered over the LEDs 116a. The gasket 114 may be a frontside gasket that, like a backplate gasket provided in a groove of the backplate 104, can help protect the light engine 100 from water and dust ingress. The gasket 114 in some embodiments may be formed from silicone, such as white silicone. The chassis 120 may be formed from a metal, such as aluminum. A thermocouple (TC) point 118 may be used to measure the temperature of the chassis 120. The TC point 118 may be located, for example, on top of the connector at the LED side.
A reflector 110 may be positioned directly adjacent to the LGP 112. The reflector 110 may in some embodiments be shaped similar to the LGP 112. In other embodiments, the reflector 110 may be formed independent of the shape of the LGP 112. As above, the reflector 110 may be formed as a substantially circular disc. The reflector 110 may be positioned adjacent to the upper surface of the LGP 112 to reflect light from the LGP 112 back toward the LGP 112.
The reflector 110 can be formed from a metal or other reflective material. In some examples, the reflector 110 can be formed from aluminum, and reflect substantially all light—e.g., having a reflectivity greater than or equal to 94% over all or a portion of the visible spectrum (e.g., having a wavelength between 400 nm and 700 nm). The reflector 110 can be attached with electrical tape or another adhesive. The electrical tape can be positioned on one or more portions of the top and bottom surfaces of the reflector 110. In some examples, tape on the top and/or bottom surface may extend radially outward past the circumferential edge of the reflector 110 and may be stuck to each other via adhesive on the tape. In some examples, the adhered tape portion may be bent approximately orthogonally to a plane of the top/bottom surface of the reflector 110, which may be bent away from the LEDs 116a.
The reflector 110 may have a first side facing the LGP 112 and a second side facing away from the LGP 112. The reflector 110 in some embodiments may be separated from a backplate 104 by one or more gap fillers 108. The gap fillers 108 may be formed from foam or another material and may have any desired shape, such as a circular disc shape or a semicircular shape (with the flat portion facing inwards). The gap filler 108 can have a thickness and durability selected to reduce or eliminate a gap between the reflector 110 and the LGP 112. Reducing or eliminating the gap can reduce or eliminate shadowing caused by the gap fillers 108. In other embodiments, the reflector 110 may only be separated along edges of the reflector 110, instead contacting the reflector backplate 104 over a substantial portion of the diameter of the reflector 110 and eliminating the gap filler 108.
The backplate 104 may be formed from a metal. The backplate 104 may be, in some embodiments, about 1.53 mm. The backplate 104 may be positioned adjacent to the reflector 110 on a side opposite the LGP 112. The backplate 104 may be connected to the chassis 120 by one or more fasteners. A cable reliever may be disposed on the backplate 104 to provide support for one or more cables used to hang or otherwise retain the light engine 100. The stress reliever can prevent tearing the electrical cables off main connection points.
A set of locator pins 122 (also called light guide alignment pins) may have matching slots in optics (not shown in
A maximum opening without the LGP 112 may be minimized or reduced to prevent electrical accessibility and therefore bypass any requirement for low-temperature impact tests to the LGP 112. The size of the light engine 100, a metal choice of the chassis 120 and/or backplate 104 and other metal components, and a spacing of the LEDs 116a may be designed to maximize or increase thermal dissipation and pass, for example, a UL8750 thermal test at a maximum power output. Flats in the chassis 120 can be designed to prevent any issue of air gaps below the LEDs 116a.
The FPC 116 may be designed such that male electrical connectors and wires that supply power to the LEDs 116a are located outside the optical path, which can improve the light-emission surface uniformity and increase the optical quality. The FPC 116 can optionally allow for curved shapes.
While only a partial cross-section of the light engine 200 is shown in
Similar to the arrangement of
In some embodiments, optics such as the LGP 212 may be disposed between at least a portion of the chassis 220 and the FPC 216. As shown in
A backplate 204 may be attached to the chassis 220 via multiple fasteners, such as screws. The screws may be disposed symmetrically around the backplate 204. For example, eight screws (and thus screw holes) may be disposed along the circumference of the backplate 204, having about a 45° angle therebetween. The backplate 204 may not be completely flat; as above, in some embodiments, the backplate 204 may have a recess formed in a center area over the reflector 210 or may have grooves formed over the reflector 210. In some embodiments, an intermediate portion of the backplate 204 may be bent at an about a 90 degree angle between the portion of the backplate 204 disposed over the outer cavity and the portion disposed over the reflector 210. The intermediate portion of the backplate 204 may be disposed over, or proximate to (e.g., within several mm of) an edge of the reflector 210. In other embodiments, the intermediate (bent) portion may be formed at an acute angle of about 45 degrees, extending over about the same range proximate to the edge of the reflector 210. Locator pins 222 may be used to retain the LGP 212 in the chassis 220.
A gasket 226 may be used, as in
In some embodiments, the distance from the FPC 216 on the chassis 220 to the LGP 212 may be about 1.5 mm, the distance between the top of the backplate 204 and the bottom of the chassis 220 may be about 32.2 mm, the width of an inner cavity of the chassis 220 in which the FPC 216 and LEDs 216a are retained may be about 11.5 mm, a thickness of the backplate may be about 1.59 mm, a distance between the top of the LEDs 216a to the reflector 210 may be about 0.51 mm, the distance between the reflector 210 and the middle of the LEDs 216a may be about 2.44 mm, the distance between the middle of the LEDs 216a and the bottom of the LGP 212 may be about 3.56 mm, the distance between the FPC 216 on the inner wall of the chassis 220 and the reflector may be about 0.71 mm, the distance between the bottom of the LGP 212 and the bottom of the chassis 220 may be about 20.3 mm, and the distance between the bottom of the cavity in the chassis 220, the length of the locator pin 222 may be about 9.53 mm and the locator pin 222 may be about 3.84 mm. As shown in
In some embodiments, the radial width of the locator pin slots 212a may be as large as possible to allow assembly tolerance and prevent the LGP 212 from contacting the locator pins 222a, 222b upon an increase in temperature due to operation of the light engine 200 and/or external environmental changes. Similarly, in some embodiments, the transverse width of the locator pin slots 212a may be relatively tight to avoid movement in the transverse direction. The upper and lower locator pins 222a may control the x position of the LGP 212, the right and left locator pins 222b may control the y position of the LGP 212, and each of the locator pins 222a, 222b may control rotation of the LGP 212. The pin slots 212a may have a radial width of about 2.5 mm, the diameter of each of the locator pins 222a, 222b may be about 1.588 mm, the width of the pin slots 212a may be about 1.66 mm, and the distance between the end of the pin slots 212a and the end of the straight portion of the pin slots 212a may be about 1.67 mm. This permits the locator pins 222a, 222b to limit thermal displacement (expansion) of the LGP 212 towards the LEDs 216a while minimizing the distance between the LGP 212 and the LEDs 216a. The distance between the LGP 212 and the LEDs 216a may be minimized to 1.5 mm under the worst case ambient heat conditions of about 40° C. due to the different materials used (in some embodiments, the LGP 212 being formed from PMMA while the chassis 220 being formed from aluminum having a CTE 3 times that of PMMA).
To simplify and limit computational time in modeling this design, it is also assumed that there is no gasket 226. The gasket 226, if desired, may be included in a second round of modeling. Contacts between components are set to be bonded, which may not be completely valid, but these contacts are minimized; “non-penetration” contacts which should be the more appropriate interface conditions do not converge. Further, when the backplate is not present, the LGP 212 sits higher than the bottom edge of the LEDs 216a so at least a portion of the LEDs 216a is visible. This, however, is expected with the gasket 226 on and no backplate pressing down on the LGP 212. Accordingly, the force used to press down the gasket 226 may be relatively high.
As indicated above, the backplate 204 may have a center disc and an outer ring circumscribing the center disc. The center disc and outer ring may be connected by an intermediate portion that extends at up to a right angle (e.g., about 30 degrees, about 45 degrees, about 60 degrees or about 90 degrees) from both the center disc and outer ring, although the angles of extension may be the same or may be different. The center disc may contact the reflector 210 and may avoid the use of the gap fillers 208.
In other embodiments, as shown in the planar view of
The light engine 300 may be disposed on a pedestal or post 340 for indoor or outdoor lighting applications. A reference notch may be used to permit the light engine 300 to be positioned correctly on the post 340 and/or components of the light engine 300 to be assembled. The reference notch may be, for example, triangular in shape, although, upon reading and understanding the disclosed subject matter, a person of ordinary skill in the art will recognize that many other shapes may be used as well. The bottom view of the light engine 300 shows an element 330 may be present between the LEDs 216a and the external environment. The element 330 may be an optical element such as a lens, a window or detector, such as a motion detector, and/or an opaque plate. A light diffuser may be formed from any material that diffuses or scatters light, e.g., a translucent material such as ground or greyed glass, or may use a diffraction element to scatter the light.
In some embodiments, the light from the light engine 300 may be distributed asymmetrically. For example, as shown in
In other embodiments, such as that shown in
The example of
In
An adhesive material 818 may be attached to the underside of a portion of the insulator 816. The adhesive material 818 may be a pressure-sensitive adhesive (PSA). The PSA is a non-reactive adhesive material that forms a bond when pressure is applied without the use of a solvent, water, or heat. The adhesive material 818 may be between about 50 μm and about 1 mm, but is typically around 100 μm. The adhesive material 818 can function like double-stick tape. The adhesive material 818 may be applied at any point, such as before the LEDs are attached. The adhesive material 818 may be applied to areas to which the multilayer structure is attached.
The insulator 816 may be formed from polyimide, or any other suitable insulating material that is sufficiently flexible when of the desired thickness. The dielectric layer 816 may be between about 25 μm and about 1000 μm, sufficient to support the conductive layer 814.
The conductive layer 814 may be formed on the dielectric layer 816. In different embodiments, the conductive layer 814 may be deposited or plated on the insulator 816. The conductive layer 814 may be formed from copper, or any other suitable conductive material. The conductive layer 814 can be patterned as desired to form traces and interconnects. The conductive layer 814 may be between about 107.5 μm and about 100 μm, nominally about 70 μm or so. In some examples, the insulator 816 and conductive layer 814 can be packaged together to form a copper-clad laminate (CCL). The insulator 816 and the conductive layer 814 can be tested together, and can withstand a specified maximum operating temperature, such as 130° C.
In some embodiments, after formation of the conductive layer 814 on the insulator 816, portions of the insulator 816 may be removed by etching or other chemical or mechanical processes to permit contact to the conductive layer 814 at appropriate locations. In other embodiments, the portions of the insulator 816 may not be removed. If a multilayer structure is used and the conductive layer 814 is not the final metal layer, a new dielectric layer may be deposited or otherwise formed on the underlying the conductive layer 814 and the process continued until the desired number of layers is reached.
In some embodiments, a reflective layer 812 may be formed on the conductive layer 814. The reflective layer 812 can be colored white, and can optionally have a reflectivity greater than or equal to a specified value, such as 70%. The reflective layer 812, the insulator 816 and conductive layer 814 can also be tested together. In some examples, these layers can withstand a specified maximum operating temperature, such as 130° C.
If a multilayer structure is not used or the conductive layer 814 is the final metal layer, a solder mask may be deposited on the topmost conductive layer 814. The solder mask may be, for example, between about 25 μm and about 50 μm. The solder mask when applied, may have openings to expose portions of the topmost conductive layer 814 to form the body contacts. The solder mask may also have openings to expose portions of the topmost conductive layer 814 to form contacts, if not formed in the insulator 816. In other embodiments, the openings in the solder mask may be formed after application of the solder mask. The LEDs or other illumination sources may then be soldered or affixed to the solder mask and/or connections otherwise made to the FPC 800.
In some asymmetrical LED embodiments, as shown in
In other asymmetrical LED embodiments, as shown in
While exemplary embodiments of the present disclosed subject matter have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art, upon reading and understanding the material provided herein, without departing from the disclosed subject matter. It should be understood that various alternatives to the embodiments of the disclosed subject matter described herein may be employed in practicing the various embodiments of the subject matter. It is intended that the following claims define the scope of the disclosed subject matter and that methods and structures within the scope of these claims and their equivalents be covered thereby.
It will thus be evident that various modifications and changes may be made to these aspects without departing from the broader scope of the present disclosure. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. The accompanying drawings that form a part hereof show, by way of illustration, and not of limitation, specific aspects in which the subject matter may be practiced. The aspects illustrated are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other aspects may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. This Detailed Description, therefore, is not to be taken in a limiting sense, and the scope of various aspects is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled.
The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in a single aspect for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed aspects require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed aspect. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate aspect.
Claims
1. A lighting system comprising:
- a chassis comprising a ridge having an inner wall that forms an inner cavity, the ridge extending from a bottom of the chassis;
- a flexible printed circuit (FPC) mounted on a wall of the inner cavity, the FPC having a leg that extends, for electrical contact, over a top of the ridge to an outer wall on an opposite side of the protrusion as the inner wall, the outer wall of the ridge defining an outer cavity, the inner cavity contained within the outer cavity, the FPC mounted on the ridge with the LEDs positioned to emit light toward a center of the inner cavity, wiring in the outer cavity connected to the FPC via an electrical connector, the FPC comprising: an insulator, an adhesive material coupled with the polyimide insulator, a conductive layer on the insulator, the conductive layer thicker than the insulator, and a high-reflectivity coverlay on the conductive layer; and
- light emitting diodes (LEDs) mounted on the FPC to contact the conductive layer.
2. The lighting system of claim 1, wherein:
- the wiring is coupled to raised bosses within the outer cavity to retain the wiring in the outer cavity.
3. The lighting system of claim 1, wherein:
- wiring of the FPC is connected to the LEDs to allow control of at least one attribute of the LEDs, the at least one attribute including color distribution and intensity distribution of light from the LEDs.
4. The lighting system of claim 1, wherein:
- the FPC encloses a circle, and
- the LEDs are disposed uniformly around the circle and configured to emit light symmetrically in all directions.
5. The lighting system of claim 4, wherein:
- the FPC comprises a first FPC formed in a first semicircle and a second FPC formed in a second semicircle, the first semicircle and the second semicircle forming the circle,
- the first FPC comprises a first set of the LEDs and the second FPC comprises a second set of the LEDs, and
- the wiring is to supply power to each of the first FPC and the second FPC, the wiring connected to opposite ends of each of the first FPC and the second FPC.
6. The lighting system of claim 5, wherein:
- the wiring connected to adjacent ends of the first FPC and the second FPC have different polarities.
7. The lighting system of claim 1, wherein:
- the FPC encloses a circle, and
- the LEDs are disposed non-uniformly around the circle such that light from the LEDs is emitted asymmetrically.
8. The lighting system of claim 7, wherein:
- the FPC comprises a first FPC formed in a first semicircle and a second FPC formed in a second semicircle, the first semicircle and the second semicircle forming the circle,
- the first FPC comprises a first set of the LEDs and the second FPC comprises a second set of the LEDs, and
- the wiring is to supply power to each of the first FPC and the second FPC, the wiring connected to opposite ends of each of the first FPC and the second FPC.
9. The lighting system of claim 8, wherein:
- a first end of the first FPC is adjacent to a first end of the second FPC,
- a second end of the first FPC is adjacent to a second end of the second FPC, and
- the first set of the LEDs is disposed more proximate to the first end of the first FPC than to the second end of the first FPC, and the second set of the LEDs is disposed more proximate to the first end of the second FPC than to the second end of the second FPC.
10. The lighting system of claim 9, wherein:
- the first set of the LEDs and the second set of the LEDs have the same number of LEDs.
11. The lighting system of claim 8, wherein:
- the wiring connected to adjacent ends of the first FPC and the second FPC have the same polarity.
12. The lighting system of claim 8, wherein:
- a first end of the first FPC is adjacent to a first end of the second FPC,
- a second end of the first FPC is adjacent to a second end of the second FPC, and
- the first set of the LEDs is centered within the first FPC such that the first set of LEDs is equidistant to the first end and the second end of the first FPC, and the second set of the LEDs is centered within the second FPC such that the second set of LEDs is equidistant to the first end and the second end of the second FPC.
13. The lighting system of claim 12, wherein:
- the first set and the second set of the LEDs have the same number of LEDs.
14. The lighting system of claim 12, wherein:
- the wiring connected to adjacent ends of the first FPC and the second FPC have different polarities.
15. The lighting system of claim 1, wherein:
- the chassis has a notch formed in an outer surface, and
- a cable stress reliever is snapped into the notch to provide stress relief for a cable used to support the lighting system.
16. A lighting engine comprising:
- a chassis having a cavity formed therein, the cavity having an inner cavity and an outer cavity defined by a ridge extending from a bottom of the chassis, the inner cavity contained within the outer cavity;
- a flexible printed circuit (FPC) mounted on a wall of the cavity with light emitting diodes (LEDs) positioned to emit light toward a center of the cavity, an outer wall of the ridge defining the outer cavity, the FPC mounted on the ridge with the LEDs positioned to emit light toward a center of the inner cavity, wiring in the outer cavity connected to the FPC via an electrical connector, the FPC comprising: an insulator, an adhesive coupled with the insulator, a conductive layer on the insulator, the conductive layer being thicker than the insulator, and a high-reflectivity coverlay on the conductive layer;
- the LEDs mounted on the FPC to contact the conductive layer;
- a light guide positioned within the cavity to receive light emitted by the LEDs through an edge of the light guide; and
- a reflector adjacent to the light guide and configured to cover the light guide entirely, the reflector configured to reflect substantially all light incident on the reflector from the light guide back toward the light guide.
17. The lighting engine of claim 16, wherein:
- the FPC comprises FPC strips configured in a circle, and
- each of the FPC strips comprises a set of the LEDs.
18. A method of fabricating a lighting system, the method comprising:
- attaching a flexible printed circuit (FPC) to a wall of an inner cavity having a circular cross-section, the inner cavity formed by a ridge extending from a bottom of a metal chassis that defines the inner cavity and an outer cavity surrounding the inner cavity, the FPC having light emitting diodes (LEDs) mounted thereon such that the LEDs are positioned to emit light toward a center of the cavity, the FPC extending over and in contact with a top of the ridge to a wall in the outer cavity, the FPC comprising: an insulator, an adhesive coupled with the insulator, a conductive layer on the insulator, the conductive layer being thicker than the polyimide insulator, and a high-reflectivity coverlay on the copper layer;
- connecting wiring in the outer cavity to the FPC in the outer cavity; and
- coupling the wiring to raised bosses within the outer cavity to retain the wiring in the outer cavity.
19. The method of claim 18, wherein:
- attaching the FPC to the wall of the inner cavity comprises attaching semicircular FPC strips to different portions of the wall to form a circular FPC structure, each of the FPC strips comprising a set of the LEDs, and
- connecting wiring in the outer cavity to the FPC in the outer cavity comprises attaching wiring to ends of each of the FPC strips, a polarity of the wiring attached to adjacent ends of the FPC being dependent on at least one of an overall distribution of the LEDs around the circular FPC structure and a distribution of the set of the LEDs within each FPC strip.
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Type: Grant
Filed: Dec 27, 2019
Date of Patent: Jul 27, 2021
Patent Publication Number: 20200341188
Assignee: Lumileds LLC (San Jose, CA)
Inventors: Frederic Stephane Diana (Santa Clara, CA), Seng-Hup Teoh (Morgan Hill, CA), Michael Wasilko (San Jose, CA)
Primary Examiner: Laura K Tso
Application Number: 16/729,131
International Classification: F21V 21/00 (20060101); F21K 9/61 (20160101); H01L 27/15 (20060101); F21V 7/00 (20060101); H05K 1/11 (20060101); F21V 23/00 (20150101); F21V 8/00 (20060101); H05K 1/02 (20060101); H05K 1/18 (20060101); F21V 7/24 (20180101); F21Y 115/10 (20160101);